The present invention relates to the art of linear motion roller bearings, and, in particular, is directed to improved linear bearing construction which minimizes impeded dynamic travel of the bearing over an axial shaft.
A typical linear bearing presently known in the art includes an outer sleeve provided in its bore with axial lands for rolling elements under load and return passages for the elements not under load, a cage installed in the bore with a plurality of circumferentially distributed projections which form channels consisting of axial races for the loaded and non-loaded rolling elements, semi-circular turnarounds connecting the races to each other in pairs, endless rows of rolling elements arranged in the channels, and end rings fixed to the ends of the outer sleeve to close off the cage at the ends.
It is known in the art to prevent rotary displacement of the cage relative to the outer sleeve by providing irregular projections, e.g., bosses and/or axial fillers, between the cage and the sleeve.
For example, U.S. Pat. No. 4,328,999 discloses a linear motion rolling bearing having an outer sleeve and a cage with loaded and return races defined therebetween, and opposite end rings molded onto the outer sleeve and formed as a unitary structure with the outer sleeve by molding or casting onto the outer sleeve. The cage 6 has radial projections 16 and 16A shown in FIGS. 1 and 3, respectively, which geometrically lock the cage against rotation within the outer sleeve, and must be provided with injectable or castable material 10B and 19, respectively.
Similarly, U.S. Pat. No. 4,139,242 shows a ball bearing with a cylindrical ball cage intermediate a shaft and outer shell, and alternately spaced longitudinal load portions and ball-return paths. The bore of the shell also has additional longitudinal recesses for receiving, with a certain amount of play, mating longitudinal ribs, which permits restricted lateral and circumferential movement of the balls relative to the shell during longitudinal movement of these balls. Different embodiments of the disclosure of U.S. Pat. No. 4,139,242 provide for limiting rotational movement by other types of radial projections fashioned as axially extending ribs which engage, with play, corresponding recesses in the shell bore surface.
U.S. Pat. No. 4,206,951 discloses a linear roller bearing having an outer housing with a central bore with a plurality of radially-inward directed axially extending projections that form races for rolling elements under load, and surfaces between projections which serve as return races. The linear bearing also has a cage within the bore of the outer housing which has, among other features, axially extending projections in its outer surface extending into corresponding grooves in the outer housing to inhibit relative rotation between the cage and the outer housing.
U.S. Pat. No. 4,278,305 describes a linear motion bearing having an outer sleeve, the bore of which houses the cage and endless rows of rolling elements. The cage has recesses which are occupied by race plates having an inner side engaging the loaded elements. Each race plate has a radial projection 13 which extends through a radial opening in the outer sleeve to maintain the plates in position.
As evident from the references described above, as well as knowledge in the art in general, in order to provide an unencumbered return path for rolling elements, relatively convoluted design features must be integrated into the primary structural elements forming the loaded and unloaded paths, and/or filler materials and/or multiple piece assembly which require time and attention, whether manual or mechanical, must be employed to effect construction. Moreover, it is believed that in the linear bearing assemblies known to date, encumbered travel over an axial shaft because of ball stagger is experienced.
It is an object of the present invention, therefore, to provide a linear bearing which overcomes the deficiencies noted above as well as other problems associated with construction and use of the linear bearings.